BRAINCAKEGenetic Recombination by Crossing Over
Each pair of homologous chromosomes have the same genes in the same loci but do not neccessarily have the same alleles. During crossing over genetic material is exchanged between homologous chromosomes.
The chromosomes become twisted around each other and the tension breaks off portions of the chromatids. The portions rejoin randomly and may reattach to the same chromosome or the other member of the pair. In this way new combinations of alleles are formed.
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Key terms in this lesson
- chromatid
- One of two identical copies of a chromosome, joined at the centromere, formed by DNA replication.
- gene
- A length of DNA that codes for a polypeptide or a functional RNA molecule, at a specific locus on a chromosome.
- allele
- One of the different versions of a gene, arising by mutation, that occupy the same locus on homologous chromosomes.
- homologous chromosomes
- A pair of chromosomes, one from each parent, that carry the same genes at the same loci but may carry different alleles.
More in Genetic Diversity
- Deletion of Bases
- Polyploidy and Hybrids
- Meiosis
- The Process of Meiosis
- Independent Segregation of Chromosomes
- Independent Segregation of Chromatids
- Number of Chromosome Combinations
- Genetic Diversity
All 19 lessons in Genetic Diversity · All AQA AS-level Biology topics